Device for shielding a spark plug and for conducting current thereto



May 24, 1938. T. c. GREEN 2,118,673

DEVICE FOR SHIELDING A SPARK PLUG AND FOR CONDUCTING CURRENT THERETOFile d Sept. 14, 1936 INVENTOR Y THOMAS C. GREEN ATTORNEY Patented May24, 1938 I I.

UNITED STATES. PATENT OFFICE DEVICE FOR SHIELDING A SPARK PLUG FORCONDUCTING CURRENT THERE- Thomas C. Green, United States Marine CorpsApplication September 14, 1936, SerialNo. 100,690

19 Claims. (Cl. 123-169) (Granted under the act otMarch s, 1883, asamended April 30,1928; 3'70 0. G. 157) My invention relates to a devicefor electrically after a period of use so that a slightmisalignshielding a spark plug and for conducting cur-, ment of theshielding conduit extending from the rent thereto. In order toeffectively shield exspark plug to the ring manifold will causetilttraneous apparatus against electrical disturhing of theupper casingelement with respect to 5 anoes caused by ignition circuits of internalcomthe lower one. When this occurs, oil, dirt, water 5 bustion enginesit is essential that the circuit be and other extraneous matter canfreely enter the completely encased by a metallic surface; that deviceenveloping and electrically shielding the the enveloping metallicsurface be grounded at spark plug with detriment to the instrumentaliitsends and at suitable intervals therebetween; ties housed therein.Furthermore, the design of and that the enveloping metallic surface beelecthese prior art devices for electrically shielding 10 tricallycontinuous throughout its length. Faila spark plug and. for conductingcurrent thereto ure of the enveloping metallic surface to propis'suchthat only a phenolic condensation proderly and effectively shieldagainst the deleterious not can be used for insulation in theirconstrucdisturbances generated by the ignition circuits tion thuspreventing the use of insulating mais caused principally by lack ofelectrical conterials having better dielectric characteristics. 15

tinuity along the enveloping metallic surface or Finally the contactscrew arrangement in these an increase in resistance-of the envelopingmeprior art devices does not always make proper tallic surface over thatat which optimum shieldcontact with the ignition wire. This results ining is obtained. This lack of electrical contiarcing which eventuallydestroys the wire and nuity or'increase in resistance of theenvelopingcauses an interruption in current conduction to 20 metallic surfacefrequently occurs in the device the spark plug. which electricallyshields the spark plug and con- With the foregoing prior artdeficiencies in ducts current thereto. view, it is an object of myinvention to provide The devices now in use for shielding spark adevicefor electrically shielding a spark plug per and lower electricallyconductive casing eleelectrical shielding properties are maintainedunments held in fluid impervious engagement by a impaired and whereinthe means-for conducting snap-spring arrangement, an insulatorinteriorly current to the spark plug is free from arcing.

secured to one of said casing elements and fab- It isanother object ofmy invention to proric'at'ed of a phenolic condensation product," andvide a durable and rugged device for electrically 30 an insulatedcurrent carrying conductor extendshielding a spark plug and forconducting ouring into the enclosure formed by the casing elerentthereto which canbe completely disassemments andcontact with which ismade by an arbled to enable the replacement of any damaged rangementincluding acontact screw. These departs and to thus insure economicalmaintevices neither effectively shield nor conduct ournance. I I rent tothe spark plug. The surfaces of the cas- It is another object of myinvention to proing element-s relied upon to provide electrical vide adevice for electrically shielding a spark continuity therebetween arepositioned exteriorly plug and for conducting current thereto wherein ofthe sealing means which forms a fluid. imthe casing elements of thedevice are held in non- 40 pervious seal between the upper and lowercastilting engagement and wherein an insulating 40 ing elements. Inconsequence thereof, these surmaterial other than a phenoliccondensation faces within a short time become covered with an productmay be employed. accumulation of dirt, oil and gasoline which im- Itis-another and furtherobject of my invenpairs or completely destroys theelectricakcontion to provide a device for electrically shielding .45tinuity between the casing elements at their a spark plug wherein thejuncture between the point of junction. This in turn renders theencasing elements of said device is maintained by tire shielding conduitfrom the spark plug to the direct and intimate metallic contact, thesaid ring manifold inoperative to accomplish its elecjuncture beingsealed against the device exterior trical shielding function.An-iexcessive amount whereby electrical continuity along and through soof maintenance'work is therefore necessary to the device is insured.keep these prior art devices reasonably effective It is another andstill further object of my infor shielding purposes. The snap-springarvention to provide a device for conducting currangement which isrelied upon to hold the upper rent to a spark plug' which is free fromarcing. and lower casing elements in engagement is Other objects andmany of the attendant adeither insufllciently strong or loses itstension vantages of this invention will'be readily applugs andconducting current thereto include upand for conducting current theretowherein the 25 preciated as the same becomes better understood byreference to the following description when considered in connectionwith the accompanying drawing wherein:

Figure 1 is a view in cross sectional elevation of the assembled deviceof my invention operatively associated with a spark plug; and

Figure 2 is a plan view of the said device.

The device of my invention for electrically shielding a spark plug andfor conducting current thereto is intended primarily for use with theshielding of spark plugs in aircraft. It is to be emphasized, however,that the device of my invention is not restricted to the aforementioneduse but may be used wherever and whenever an efllcient device is desiredfor electrically shielding a spark plug and for conducting currentthereto.

Turning now to the drawing, there is shown at I a lower electricallyconductive casing element having a flange 2 at one end thereof adaptedto contact the lower portion of the spark plug 3 and an annular threadedjunction member 4 at the upper end thereofand'forrning part of thecasing element. end thereof detachably associated with the annularmember 4 of the lower casing element and has at the other end thereof atubular projection 6 through which the ignition cable 1 passes. Theouter end of the tubular projection 6 is adapted for connection to theshielding conduit which passes to the ring manifold. For joining theouter end of the tubular projection 6 to the shielding conduit I preferto employ the electrically continuous connector disclosed in myapplication Serial No. 100,687, filed 14 September 1936 of which thefemale connector part a is here shown. The female connector part II andthe annular member 4 may be assembled with their respective casingelements 5 and I by sweating the same thereto with solder, by brazing,silver soldering, or similar and equivalent processes. Instead, however,the female connector part 8 and the annular member 4 may be fabricatedintegral with their respective casing elements if desired. Theelectrically conductive casing elements I and I may advantageously befashioned from brass, bronze, aluminum alloy or mild stainless steel orany other suitable metal or alloy.

The lower and upper electrically conductive casing elements I and 5 areprovided at their contiguous ends with surfaces 9 and I0, respectively,which are in intimate and direct metallic contact to thus insureelectrical continuity between the casing elements. While these surfacesof contact are shown as surface portions of a sphere, I do not desire tobe restricted thereto since other inclined contact surfaces may beemployed within the purview of my invention and will readily suggestthemselves to those skilled in the art, conical surfaces and pyramidalsurfaces being illustrative but not restrictive of such other inclinedsurfaces. The lower and upper casing elements I and 5 are also providedwith bearing faces II and I2, respectively, which extend from adjacentthe outermost edge of contact between the contact surfaces 9 and Ioutwardly of the device. A fluid impervious gasket I3 is seatedin agroove I4 in the end of the casing element and is interposed between thehearing faces II and I! to thus be engaged and compressed thereby. Thisgasket may be fabricated of asbestos, fibre, synthetic rubber, rubber,special gasket paper or any other suitable material so long as thematerial chosen 8 sub- An upper casing element 5 has one stantiallyfluid impervious, will withstand the weather and be reasonably resistantto fluids such as, for example, gasoline, oil and water.

In order to insure a direct and intimate metallic contact between thecontacting surfaces 9 and III of the casing elements and a compressionof the gasket I3, the casing elements I and 5 have been provided attheir contiguous ends with ex* ternal screw threads I5 and a flange I6respectively which are adapted to engage, internal screw threads I! anda complemental flange I8 of a coupling sleeve or nut I9. The couplingnut I9 is octagonally or otherwise shaped to permit the use of a wrenchfor tightening purposes. In addition to holding the contact surfaces 9and III of the casing elements in intimate and direct metallic contactthe coupling sleeve or nut I9 serves also to cause a compression of thefluid impervious gasket I3 as well as to furnish some protection to thesaid gasket and to provide a secondary electrically conductive pathbetween the casing elements I and 5. It is to be observed that thecross-sectional area of the sleeve or nut I9 and of the casing portionswhich form a juncture at their contacting surfaces 9 and I0 is greaterthan the cross-sectional area of the remaining casing parts. Thisconstruction of the nut and casing portions at the juncture therebetweenserves to provide a heat dissipating extension which among other thingsprevents overheating of the portion of the ignition cable I housedwithin the tubular projection 6. Furthermore, the greater diameter andthe three exposed sides of the coupling sleeve or nut I9 provide forgreater heat dissipation in it than at the Juneture enclosed thereby,thus producing a shrinking effect which further tightens the junctureand avoids the possibility of the nut loosening and backing off.

Removably and interiorly secured to the upper casing element 5 is theinsulator 20 which may be fashioned of any suitable ceramic or phenolicinsulating material. Isolantite and pyrex, however, are consideredpreferable to bakelite for this purpose. The insulator is provided atits upper end with a plurality of recesses II which are adapted toreceive the cylindrical portions 22 of set screws 23 which, as shown,have threads at their upper ends which are adapted to engage the wallsof threaded apertures in the upper casing element 5 to thus removablysecure the insulator in place. The heads of these set screws 23 may beprovided with holes through which safety wire can be passed to preventthe screws from backing out. Since, however, it is necessary to removethe screws only to replace the insulator 20 their heads may be solderedto the upper casing element Ii if desired instead of using the safetywire previously discussed. While I have shown three set screws forsecuring the insulator in place, only two need be employed which in thiscase would be diametrically positioned with respect to each other.

The insulator 20, as shown, is provided with a passageway 24 whichextends from its upper end and terminates inwardly thereof in a recess'25 and annular groove 26. The distance in all directions over andthrough the insulator along which the ignition current would travel toreach the insulator. The inner surface of the depend-- ing portion 21 ofthe insulator 29' may-be fashf ioned with annular serrations to increasethe surface distance across it if this is deemed desirable. In addition,if desired, the upper portion of the insulator may be provided withcells or foramina to lighten the same. Because of the simplicity indesign of my insulator 20, I am enabled to use ceramic insulatingmaterials-in fabricating the same and am not limited to the use ofphenolic condensation products which have lower dielectriccharacteristics.

The ignition cable or insulated current carrying conductor 1 extendsfrom within the tubular projection 6 into and through the passageway 24of the insulator to within the insulator recess 25 and has itsinsulation terminating short of the end thereof leaving a portion 28thereof uninsulated and exposed. An electrically conductive body 29 isprovided with major and minor recesses 33 and 3i, respectively, whichare interconnected by a small passageway 32, the major recess 30receiving the conductor with its insulation adjacent the end thereof andthe other and minor recess receiving the uninsulated and exposed endportion 28 of the conductor which is threaded through the passageway 32.The uninsulated and exposed end portion 28 of the conductor extendinginto the minor recess 3| of the terminal 29 is pressed into an intimate,mechanically secure, electrical contact with the recess walls and ispreferably, although not necessarily, soldered in place therein.Although the electrically conductive body or terminal 29 is ,shownsubstantially spherical in shape, it is evident that it may have anyother shape which will make a good electrical contact with the coiled orconvoluted member to be described hereinafter. Thus the terminal 29serves both to carry the ignition current and to secure the end of theignition wire while eliminating any possibility of arcing with attendantdestruction of the wire and consequent interruption of current flow tothe spark plug.

For completing the current path from the cable terminal fd'to the sparkplug 3, I employ a convoluted or coiled, resilient electricallyconductive .member 33 having a plurality of convolutions 34 and 35 atone end thereof, the convolution 34 of larger diameter being seated inthe annular groove 26 of the insulator and the convolution 35 of lesserdiameter being in intimate and direct electrical contact with theterminal 29 to thus insure electrical continuity therebetween. Theconvolution 35 of lesser diameter also serves to hold the terminal 29 inplace within the insulator recess 25. The lower and other end of theresilient, coiled member 33 is provided with a plurality of convolutions36 which serve to make electrical contact with the spark plug andreceive within their confines a portion 31 thereof. In operation theresilient member 33 is compressed to thus insure electrical continuityfrom the electrically conductive body or terminal 29 to the spark plug 3and hence unimpaired current conduction thereto. It is to be observedthat the outer curved surface of the terminal is of advantage in thatthe convolution 35 of lesser diameter conforms itself readily theretowith the result that intimate and eflicient electrical contacttherebetween is assured.

In use the coupling nut I9 is assembledwith the upper casing element 5adjacent the end thereof. The casing elements 5 and l are then tion onthe upper casing element 5 is wedged into the corresponding. recess inthe lower casing element I, thus providing direct electrical conti--nuity through-and along the casing elements. Simultaneously with thetightening of the nut l3 the sides of the gasket l3 are compressedbetween the bearing faces It and I2, thus sealing within its confinesthe surfaces of contacts 3 and ill of the casing elements against theexterior of the device and providing fluid tight integrity against theintroduction of extraneous materials such as gasoline, oil and moisture.Furthermore, since the resilient, electrically conductive member 33 iscompressed as incidental to the securing of the casing. elementstogether, electrical continuity from the terminal 29 to the spark plug 3is assured.

Thus it is seen that I have provided a durable and rugged device forelectrically shielding a spark plug and for conducting current thereto,

from arcing and is capable of being completely disassembled to enablethe replacement of damaged parts to thereby insure economicalmaintenance.

According to the provisions of the patent statutes, I have set forth theprinciple and mode of operation of my invention and have illustrated anddescribed what I now consider to represent its best embodiment. However,I desire to have it understood that within the scope of the appendedclaims the invention may be practiced otherwise than as specificallyillustrated and described.

The invention described herein may be manu factured and used by or forthe Governmentof the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

Having thus set forth and disclosed the nature of this invention, Whatis claimed is:

1- A device for electrically shielding a spark plug and for conductingcurrent thereto com,- prising in combination an electrically conductivecasing element having a flange at one end thereof adapted to contact thelower portion of a spark plug and a contact surface and bearing face atthe other end thereof, a second electrically conductive casing elementhaving a tubular projection at one end thereof for connection with ashielding conduit and a contact surface and bearing face at the otherend thereof, the surfaces of contact of said casing elements being in 1intimate surfaces of said casing elements against the exterior of thedevice, one of said casing elements being provided with exterior threadsand the re maining element with a flange, a sleeve having a complementalflange at one end operable to en-- gage the flange on one of said casingelements and interior threads at the other end to cooperatively engagethe exterior threads on the other of said casing elements, said sleevefunctioning to hold said casing elements in engagement at their surfacesof contact and to cause the hearing faces to abut against and compressthe deformable means interposed therebetween whereby to insure theformation of a. fluid impervious enclosure by said casing elements aswell as an electrically continuous and protected juncture therebetween,a ceramic insulator interiorly and removably secured to said secondmentioned casing element and provided with a passageway which terminatesat its inner end in a recess and an annular groove, an insulated currentcarrying conductor having its insulation terminating short of the endthereof leaving a portion of the conductor uninsulated and exposed andextending from within the tubular projection of said second mentionedcasing element into and through the passageway of the insulator towithin the insulator recess, an electrically conductive body having acurved outer surface and a plurality of recesses one of which receivesthe conductor with its insulation adjacent the end thereof and the otherof which receives the uninsulated and exposed end portion of theconductor with the recess walls in good electrical contact therewith, aconvoluted, resilient, elec trically conductive member having aplurality of convolutions at one end thereof one of which is positionedwithin the annular groove of the insulator and the other of which is inintimate contact with the curved outer surface of the electricallyconductive body, and a plurality of convolutions at the other end ofsaid convoluted member which are adapted to make electrical contact withthe spark plug and receive within their confines a portion thereof, thesaid convoluted, resilient member when in use being compressed to thusinsure electrical continuity from the conductive body to the spark plugand hence unimpaired current conduction thereto.

2. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination a plurality of electricallyconductive casing elements each having at one end thereof a contactsurface and a bearing face the contact surfaces of which are in intimateelectrical engagement, deformable means interposed between the bearingfaces of said casing elements and adapted to be engaged thereby forsealing the area of contact at the surfaces of said casing elementsagainst the exterior of the de- ;vice, one of said casing elements beingprovided with exterior threads and the remaining element with a flange,a sleeve having a complemental flange at one end operable to engage theflange on one of said casing elements and interior threads at the otherend to cooperatively engage the exterior threads on the other of saidcasing elements, said sleeve functioning to hold said casing elements inengagement at their surfaces of contact and to cause the bearing facesto abut against and compress the deformable means interposedtherebetween whereby to insure the formation of a fluid imperviousenclosure by said casing elements as well as an electrically continuousand protected juncture therebetween, a ceramic insulator interiorly andremovably secured to one of said casing elements and provided with apassageway which terminates at its inner end in a recess and an annulargroove, an insulated current carrying conductor having its insulationterminating short of the end thereof leaving a portion of the conductoruninsulated and exposed and extending into and through the passageway ofthe insulator to within the insulator recess, an electrically conductivebody having a curved outer surface and a plurality of recesses one ofwhich receives the conductor with its insulation adjacent the endthereof and the other of which receives the uninsulated and exposed endportion of the conductor which is soldered in place therein, aconvoluted. resilient, electrically conductive. memher having aplurality of convolutions at one end thereof one of which is positionedwithin the annular groove of the insulator and the other of which is inintimate contact with the curved outer surface of the electricallyconductive body, and a plurality of convolutions at the other end ofsaid convoluted member which are adapted to make electrical contact withthe spark plug and receive within their confines a portion thereof, thesaid convoluted, resilient member when in use being compressed to thusinsure electrical continuity from the conductive body to the spark plugand hence unimpaired current conduction thereto.

3. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element having a flange at one end thereof adapted to contact thelower portion of a spark plug and a contact surface and bearing face atthe other end thereof, a second electrically conductive casing elementhaving a tubular projection at one end thereof for connection with ashielding conduit and a contact surface and bearing face at the otherend thereof, the surfaces of contact of said casing elements being inintimate electrical engagement, deformable means interposed between thebearing faces of said casing elements and adapted to be engaged therebyfor sealing the area of contact at the surfaces of said casing elementsagainst the exterior of the device, one of said casing elements beingprovided with exterior threads and the remaining element with a flange,a sleeve having a complemental flange at one end operable to engage theflange on one of said casing elements and interior threads at the otherend to cooperatively engage the exterior threads on the other of saidcasing elements, said sleeve functioning to hold said casing elements inengagement at their surfaces of contact and to cause the bearing facesto abut against and compress the deformable means interposedtherebetween whereby to insure the formation of a fluid imperviousenclosure by said casing elements as well as an electrically continuousand protected juncture therebetween, a ceramic insulator interiorly andremovably secured to said second mentioned casing element and providedwith a passageway which terminates at its inner end in a recess and anannular groove, an insulated current carrying conductor having itsinsulation terminating short of the endthereof leaving a portion of theconductor uninsulated and exposed and extending from within the tubularprojection of said second mentioned casing element into and through thepassageway of the insulator to within the insulator recess, anelectrically conductive body having a curved outer surface and aplurality of recesses one of which receives the conductor with itsinsulation adjacent the-end thereof and the other of which receives theuninsulated and exposed end portion of the cone ductor with the recesswalls in good electrical contact therewith, a convoluted, resilient,electrically conductive member having a plurality of convolutions at oneend thereof one of which is posi- -tioned within the annular groove ofthe insulator and the other of which is in intimate contact with thecurved outer surface of the electrically conductive body, and aplurality of convolutions at the other end of said convoluted memberwhich are adapted to make electrical contact with the spark plug andreceive within their confines a portion thereof, the said convoluted,resilient memberwhen in use being-compressed to thus insure electricalcontinuity from the conductive body to the spark plug and henceunimpaired current conduction thereto, and the said casing elements attheir juncture as well as the sleeve for maintaining the juncture havinga crosssectional area which is greater than that of the remainingportions of said casing elements to thus provide a heat dissipatingextension for preventing overheating of that portion of the insulatedcurrent carrying conductor within the tubular projection of said secondmentioned casing element.

4. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate electrical contact with a second electricallyconductive casing element, deformable means interposed between saidfirst and second mentioned casing elements adjacent the outermost edgeof contact therebetween for sealing the area of contact between saidelements against the exterior of said device, means for holding saidcasing elements in engagement and for causing a compression of thedeformable means interposed therebetween to thereby insure the formationof a fluid impervious enclosure by said casing elements as well as anelectrically continuous and protected juncture therebetween, a ceramicinsulator interiorly and removably secured to one of said casingelements and provided with a passageway which terminates at its innerend in a recess, an insulated current carrying conductor having aportion at the end thereof uninsulated and exposed and extending intoand through the passageway of the insulator to within the insulatorrecess, an electrically conductive body having a recess and a curvedouter surface, the said recess receiving the uninsulated and exposed endportion of the conductor which is soldered in place therein, aconvoluted, resilient, electrically conductive member having a pluralityof convolutions at one end thereof, one of which is in engagement withthe insulator and the other of which is in intimate contact with thecurved outer surface of the electrically conductive body, and the otherend of said convoluted member being shaped to provide a mechanicallysecure and electrically eflicient contact with the spark plug, the saidconvoluted, resilient member when in use being compressed to thus insureelectrical continuity from the conductive body to the spark plug andhence unimpaired current conduction thereto.

5. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate electrical contact with a second electricallyconductive casing-element, deformable means interposed between saidfirst and second mentioned casing elements for sealing the area ofcontact between said elements against the exterior of said device, meansfor holding said casing elements in engagement and for causing acompression of the deformable means interposed therebetween to therebyinsure the formation of a fluid impervious enclosure by said casingelements as well as an electrically continuous and protected juncturetherebetween, a ceramic insulator interiorly and removably secured toone of said casing elements and provided with a passageway whichterminates at its inner end in, a

recess, an insulated current carrying conductor having a portion at theend thereof uninsulated and exposed and extending into and through thepassageway of the insulator to within the insulator recess, anelectrically conductive body having a recess and a curved outer surface,the said recess receiving the uninsulated and exposed end portion of theconductor which is soldered in place therein, a convoluted, resilient,electrically conductive member in engagement with the insulator andhaving a convolution at one end thereof in intimate contact with thecurved outer surface of the electrically conductive body and the otherend thereof shaped to provide a mechanically secure and electricallyeflicient contact with the spark plug, the said convoluted, resilientmember when in use being compressed to thus insure electrical continuityfrom the conductive body to the spark plug and hence unimpaired currentconduction thereto.

6. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate electrical contact with a second electricallyconductive casing element, means for sealing the area of contact betweensaid casing elements against the exterior of said device, and means forholding said casing elements in engagement to thereby insure theformation of a fluid impervious enclosure by said casing elements aswell as an electrically continuous and protected juncture therebetween,a

ceramic insulator interiorly secured to one of said casing elements andprovided with a recess, an insulated current carrying conductor havingone end thereof extending into the insulator recess and having the saidend provided with an electrically conductive terminal having a' curvedouter surface and electrically continuous with the conductor, aconvoluted, resilient, electrically conductive member in engagement withthe insulator and having a convolution at one end thereof in intimatecontact with the curvedouter surface of the electrically conductiveterminal and the other end thereof shaped to provide a mechanicallysecure and electrically efiicient contact with the spark plug.

7. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate and direct, electrical contact with a secondelectrically conductive casing element, means for holding said casingeleb vments in engagement and for sealing the area of contacttherebetween against the exterior of said device to thereby insure theformation of a fluid impervious enclosure by said casing elements aswell as an electrically continuous and protected juncture therebetween,insulating means interiorly secured to one of said casing elements andprovided with ,a recess, an insulated current carrying conductor havingone end thereof electrically continuous with an electrically conductiveterminal having a curved outer surface and extending into the recess ofsaid insulating means, and a resilient, electrically conductive memberhaving a convolution at one end thereof in intimate contact with thecurved outer surface of the electrically conductive terminal and theother end thereof shaped to provide a mechanically secure andelectrically eflicient contact with the spark plug.

8. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate and direct, electrical contact with a secondelectrically conductive casing element, means for holding said casingelements in engagement and for sealing the area of contact therebetweenagainst the exterior of said device to thereby insure the formation of afluid impervious enclosure by said casing elements as well as anelectrically continuous and protected juncture therebetween, insulatingmeans interiorly secured to one of said casing elements and providedwith a recess, an insulated current carrying conductor having one endthereof soldered to an electrically conductive terminal having a curvedouter surface and extending into the recess of said insulating means,and a resilient, electrically conductive means having one end thereof inintimate contact with the curved outer surface of the electricallyconductive terminal and the other end thereof operable to electricallycontact the spark plug.

9. A device for electrically shielding a spark plug and for conductingcurrent thereto comprising in combination an electrically conductivecasing element in intimate and direct, electrical contact with a secondelectrically conductive casing element, means for holding said casingelements in engagement and for sealing the area of contact therebetweenagainst the exterior of said device to thereby insure the formation of afluid impervious enclosure by said casing elements as well as anelectrically continuous and protected juncture therebetween, and meansfor conducting current to the spark plug, said last mentioned meansincluding an electrically conductive terminal electrically continuouswith an insulated current carrying conductor and in in-- timateelectrical contact with a resilient electrically conductive member.

10. A device for electrically shielding a spark plug comprising incombination an electrically conductive casing element in intimate anddirect, electrical contact with a second electrically conductive casingelement, and means for holding said casing elements in engagement andfor sealing the area of contact therebetween against the exterior ofsaid device to thereby insure the formation of a fluid imperviousenclosure by said casing elements as well as an electrically continuousand protected juncture therebetween.

11. A'device for electrically shielding a spark plug comprising incombination an electrically ing elements to thus provide a heatdissipating extension.

12. A device for electrically shielding a spark plug comprising incombination an electrically conductive casing element in intimate anddirect, electrical contact with a second electrically conductive casingelement, deformable means interposed between said flrst and secondmentioned casing elements for' sealing the area of contact between saidelements against the exterior of said device, and means for holding saidcasing casing elements as well as an electrically continuous andprotected juncture therebetween.

13. A device for electrically shielding a spark plug comprising incombination an electrically conductive casing element having a contactsurface and a bearing face at one end thereof, a second electricallyconductive casing element having a contact surface and a bearing face atone end thereof, the surfaces of contact of said casing elements beingin intimate and direct electrical engagement, deformable meansinterposed between the bearing faces of said casing elements and adaptedto be engaged thereby for sealing the area of contact at the surfaces ofsaid casing elements against the exterior of the device, and means forholding said casing elements in engagement and for causing the bearingfaces to abut against and compress the deformable means interposedtherebetween whereby to insure the formation of a fluid imperviousenclosure by said casing elements as well as an electrically continuousand protected juncture therebetween.

14. A device for conducting current to a spark plug comprising incombination a plurality of detachably connected casing elements, aninsulator interiorly and removably secured to one of said casingelements and provided with a passageway which terminates at its innerend in a recess and an annular groove, an insulated current carryingconductor having its insulation terminating short of the end thereofleaving a portion of the conductor uninsulated and exposed and extendinginto and through the passageway of the insulator to within the insulatorrecess, an electrically conductive body having a curved outer surfaceand a plurality of recesses one of which receives the conductor with itsinsulation adjacent the end thereof and the other of which receives theuninsulated and exposed end portion of the conductor with the recesswalls in good electrical contact therewith, a convoluted resilient,electrically conductive member having a plurality of convolutionsht oneend thereof one of which is positioned within the annular groove of theinsulator and the other of which is in intimate contact with the curvedouter surface of the electrically conductive body, and a plurality ofconvolutions at the other end of said convoluted member which areadapted to make electrical contact with the spark plug and receivewithin their confines a portion thereof, the said convoluted, resilientmember when in use being compressed to thus insure electrical continuityfrom the conductive body to the spark plug and hence unimpaired currentconduction thereto.

15. A device for conducting current to a spark plug comprising incombination a plurality of detachably connected casing elements, aninsulator interiorly secured to one of said casing elemerits andprovided with a passageway which terminates at its inner end in arecess, an insulated current carrying conductor having a portion at theend thereof uninsulated and exposed and extending into and through thepassageway of the insulator to within the insulator recess, anelectrically conductive body having a recess and a curved outer surface,the said recess receiving the uninsulated and exposed end portion of theconductor which is soldered in place therein, a convoluted, resilient;electrically conductive member having a plurality of convolutions at oneend thereof one of which is in engagement with the insulator and theother of which is in intimate contact with the curved outer surface ofthe electrically conductive body, and the other end of said convolutedmember being shaped to provide a mechanically secure and electricallyefficient contact with the spark plug, the said convoluted, resilientmember when in use being compressed to thus insure electrical continuityfrom the conductive body to the spark plug and hence unimpaired currentconduction thereto.

16. A device for conducting current to a spark plug comprising incombination a plurality of detachably connected casing elements, aninsulator lnteriorly secured to one of said casing elements and providedwith a recess, an insulated current carrying conductor having one endthereof extending into the insulator recess and having the said endprovided with an electrically conductive terminal having a curved outersurface and electrically continuous with the conductor, a convoluted,resilient, electrically conductive member in engagement with theinsulator and having a convolution at one end thereof in intimatecontact with the curved outer surface of the electrically conductive Iterminal and the other end thereof shaped to provide a mechanicallysecure and electrically eflicient contact with the spark plug.

17. A device for conducting current to a spark plug comprising incombination a plurality of detachably connected casing elements, aninsulated current carrying conductor having one end thereof extendinginto the enclosure formed by said casing elements, the said end beingprovided with an electrically conductive terminal having a curved outersurface and electrically continuous with the conductor, and a resilient,electrically conductive means having one end thereof in intimate contactwith the curved outer surface of the electrically conductive terminaland the other end thereof operable to electrically contact the sparkplug.

18. A device for conducting current to a spark plug comprising incombination a plurality of de tachably connected casing elements, aninsulated current carrying conductor having one end thereof extendinginto the enclosure formed by said casing elements, the said end beingprovidedwith an electrically conductive terminal permanently securedthereto having a curved outer surface and electrically continuous withthe conductor, and a resilient electrically conductive member having aconvolution at one end thereof in intimate contactwith the'curved outersurface of the electrically conductive terminal and the other endthereof shaped to provide a mechanically secure and electricallyefficient contact with the spark plug.

19. A device for conducting current to a spark plug comprising incombination means defining an enclosure, insulating means disposedwithin said enclosure and provided with a recess, an insulated currentcarrying conductor having one end thereof extending into the aforesaidrecess, the said end being provided with an electrically conductiveterminal having a curved outer surface 'and electrically continuous withthe conductor, and electrically conductive means engaging saidinsulating means and having a portion thereof in intimate contact withthe curved outer surface of the electrically conductive terminal andanother portion thereof operable to electrically contact the spark plug.

THOMAS C. GREEN.

